Evenly grease a 9 x 9-inch baking dish with vegetable oil or any neutral oil using a paper towel.
Cook short grain rice according to package instructions in your rice cooker or on the stove top.
Preheat oven to 500 degrees F.
To season the rice: Transfer cooked hot rice to a large bowl. Season rice with salt, sugar and rice vinegar and mix with a rice paddle. Then evenly spread the rice and firmly pack the rice into the baking dish.
Sprinkle sesame seeds and furikake over the seasoned rice.
To make the spicy tuna mixture: Open canned tuna and strain out as much of the liquids as possible using a fine sieve and a fork. Transfer strained tuna to a medium-sized bowl and mix with Japanese mayo, sriracha sauce, and salt. Evenly spread the spicy tuna mixture over the rice.
Then peel and thinly slice avocados. Spread avocado slices over the tuna layer.
Generously drizzle Japanese mayo and sriracha sauce over the avocado.
Broil in oven for 10 minutes until the sauce is bubbling and golden brown. Remove from the oven and garnish with green onions.
Slice the sushi bake with a wet knife into 20 pieces and scoop a portion of the filling into a small sheet of nori. Enjoy!
